Phase Transition of CuS 1- xSe x (0 < x < 1) Studied by Powder X-Ray Diffractometry

The temperature dependence of lattice parameters for CuS 1- x Se x (0 < x < 1) is presented by powder X-ray diffractometry. A hexagonal/orthorhombie transition was observed in the whole range of x. The high temperature hexagonal c/a of the compound increases with increasing x until x = 0.6 and decreases above x = 0.6. This composition dependence of c / a is due to the preferential occupation of Se at S2 sites in the Cu 2S 2 sheet which is previously reported by a Raman spectroscopic study of the system. The transition temperature increases from 55 K for x = 0 to 398 K for x = 1 with increasing x and is closely related to the occupancy of Se at the S2 sites.